SELF-COMPATIBILITY, AUTONOMOUS SELF-POLLINATION, AND INSECT-MEDIATED POLLINATION IN THE CLONAL SPECIES IRIS VERSICOLOR

In clonal species, sexual and asexual systems interact to create a hierarchy of reproduction. For example, self-pollination can occur within pollination units, flowers, ramets, or clones. We investigated the reproductive biology of a natural population of Iris versicolor using pollination manipulations and observations of pollinator behaviour. We found that (i) individuals were completely self-compatible, (ii) selfing rates were close to 100%, (iii) autonomous self-pollination can occur through stigma-anther contact or wind action, (iv) most seed and fruit set can be accounted for by insect pollination, and (v) facilitated self-pollination likely occurs because pollinators frequently visit more than one pollination unit within a flower. Our observations showed that flowers pass through three stages: (i) a male stage (in which pollen is freely available, but stigmas are inaccessible, preventing autogamy); (ii) a female stage (in which stigma flaps have reflexed and are receptive, but pollinators may have already removed most pollen grains, structuring opportunities for geitonogamy); and (iii) a strongly autogamous stage (in which stigma flaps have curled back to contact anthers, leading to delayed autonomous self-pollination). This hierarchy of relatedness among mates determines the genetic consequences of vegetative and sexual reproduction in clonal plants and influences their evolution.